Numerous materials first have to be dried before further processing or packing. Furthermore, especially if the material is a food product, the drying process must as far as possible be performed in such a way that any contact between the material to be dried and germs or other micro-organisms can be ruled out. With conventional drying methods, in which there is contact between the material and dry air, it is, however, difficult to achieve general sterility. Furthermore, the drying inevitably involves a certain loss of volatile components, which escape from the material because of the elevated drying temperature.
The problem of the invention consists in providing a method and an apparatus which make it possible to dry a material efficiently without this entailing any contamination with undesirable germs and without any excessive loss of volatile components occurring.